Protection of Microgrid using Coordinated Directional Overcurrent Relays

Abstract

As decentralization of generation is gaining popularity nowadays, microgrid finds its application in electrical power system. Microgrid can be termed as smaller version of large power grids. Microgrid is connected with distributed energy resources, along with storage devices and the loads, connected in parallel. Microgrid is capable of operating in grid connected mode or independent i.e. islanded mode. Its purpose is to supply reliable and quality energy in both modes, grid connected and islanded mode. Because of generators at all levels and two mode operation protection of microgrid becomes tricky. Relay coordination ensures that device closest to fault operates first. In the proposed system, PSCAD/EMTDC has been used to simulate a system consisting of microgrid connected to several distributed resources. A protection scheme has been designed which includes directional over current relays. These relays are coordinated in terms of their operating time.